The Brightseat Formation is an exposure of marine sedimentary rock beds of Upper

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

/Lower

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

age (65 MY to 55.5 MY), in

Landover, Maryland Landover is an unincorporated community and census-designated place in Prince George's County, Maryland, United States. As of the 2020 census it had a population of 25,998. Landover is contained between Sheriff Road and Central Avenue to the so ...

. The exposure is located at Brightseat Road between Sheriff and Landover Roads. The site is currently owned by the

Maryland-National Capital Park and Planning Commission The Maryland-National Capital Park and Planning Commission (M-NCPPC) is a bi-county agency that administers parks and planning in Montgomery and Prince George's counties in Maryland. History The commission was formed in 1927 by the Maryland ...

. It was given its name by R.R. Bennett and G.G. Collins in 1952. According to the Maryland Geologic Survey, the exposure consists of "Gray to greenish-gray,

micaceous Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is ...

argillaceous Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay mineral ...

, sparsely glauconitic, fine- to coarse-grained sand, locally indurated

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an a ...

beds; phosphatic pebbles; thickness 0 to 20 feet."

Research

Available research on the

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

and

fauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as ''biota''. Zoo ...

of the Brightseat Formation is decades-old. In 1968, thirty-five species of minute crustaceans,

ostracodes Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typical ...

, mostly cytheraceans, were found at outcrops of the Brightseat Formation, including 13 new species. The presence of

otoliths An otolith ( grc-gre, ὠτο-, ' ear + , ', a stone), also called statoconium or otoconium or statolith, is a calcium carbonate structure in the saccule or utricle of the inner ear, specifically in the vestibular system of vertebrates. The s ...

, calcareous secretions that accumulate within the auditory chambers of

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartila ...

, indicate the presence of fish fauna in the formation. The Brightseat Formation has also yielded three taxa of

sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhe ...

s: ''

Taphrosphys ''Taphrosphys'' is an extinct genus of bothremydid pleurodiran turtle that was discovered Angola, Morocco and the United States.E. D. Cope. 1869. The fossil reptiles of New Jersey. American Naturalist 3:84-91 The genus consists of type species '' ...

sulfates'' (Leidy), ''Agomphus'' sp., and ''

Osteopygis ''Osteopygis'' is a genus of extinct turtle. ''Osteopygis'', as traditionally seen, is a chimera: the postcrania (including the holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when t ...

emarginatus'' Cope.Weems, R. E. 1988. Paleocene turtles from the Aquia and Brightseat formations, with a discussion of their bearing on sea turtle evolution and phylogeny. Proceedings of the Biological Society of Washington 101:109–145.

References

{{Reflist

External links

Maryland Geological Survey: Coastal Plains Rocks and Sediments
Upper Cretaceous Series of North America Landover, Maryland Paleogene Maryland Paleontology in Maryland